The use of aminopolycarboxylates as laundry detergent additives is generally disclosed in the art. For example, the priro art described laundry detergent compositions which include nitrilotriacetates (NTA), ethylendediaminetetraacetates (EDTA). diethylenetriaminepentaacetates (DTPA), and hydroxyethylethylenediaminetriacetates (HEDTA), and triethylenetetraminehexaacetic acid (TTHA).
U.S. Pat. No. 4,560,491, Curry and Edwards, issued Dec. 24, 1985, discloses laundry detergent compositions, essentially free of phosphate detergency builders, containing an aluminosilicate or organic detergency builder and from about 0.5% to about 10% by weight of the chelant, HEDTA. The list of suitable organic detergency builders disclosed includes aminopolycarboxylates, such as NTA, EDTA and DTPA. Examples I and II disclose liquid detergent compositions containing DTPA and HEDTA. Example III disclosed a grandular detergent composition containing NTA and HEDTA.
U.S. Pat. No. 4,397,776, Ward, issued Aug. 9, 1983, discloses liquid laundry detergent compositions, having a pH between 9 and 13, containing alpha-amine oxide surfactants and from about 0.01% to about 25% by weight of a heavy-metal chelating agent. The chelating agent sequesters heavy-metal ions and thus enhances the stability of the alpha-amine oxides. The preferred chelating agents include aminopolycarboxylates, such as NTA, EDTA, DTPA, and HEDTA.
U.S. Pat. No. 3,920,564, issued Nov. 18, 1975, discloses softener/detergent formulations containing surfactants, quaternary ammonium or diamine fabric softeners, and a builder salt selected from aminopolycarboxylates and/or sodium citrate. Examples of suitable aminopolycarboxylates include NTA, EDTA and HEDTA.
U.S. Pat. No. 3,151,084, Schiltz et al, issued Sept. 29, 1964, discloses alkylbenzenesulfonate-containing detergent compositions in which solubility is said to be improved by the addition of 0.25%-4% of a mixture of EDTA and a solubilizing agent selected from salts of N,N-di(2-hydroxyethyl) glycine, iminodiacetic acid, NTA and HEDTA.
U.S. patent application Ser. No. 880,605, Lewis, filed June 30, 1986, discloses laundry detergent compositions, essentially free of peroxygen bleach compounds, containing a surfactant, a builder, and from about 0.3% to about 10% by weight of the chelant, TTHA. Example 1 discloses granular detergent compositions containing NTA, EDTA, DTPA and TTHA.
None of these patents or applications disclose detergent compositions which contain EDDS. Moreover, the aminopolycarboxylates disclosed in those patents or applications are not biodegradable.
The art also discloses methods of synthesizing EDDS. For example, U.S. Pat. No. 3,158,635, Kezerian and Ramsey, issued Nov. 24, 1964, discloses methods of preparing compounds having the formula: ##STR1## wherein Z.sub.1 and Z.sub.2 are the same or different bis-adduction residues of unsaturated polycarboxylic acids and salts thereof, and R.sub.5 is an alkylene or alkylene-phenylene group. These compounds are taught to be useful for removing rust and oxide coating from metals. If ##STR2## then the compound is EDDS. Example 1 discloses a method of synthesizing EDDS from maleic anhydride and ethylenediamine.
Springer and Kopecka, Chem. Zvesti. 20(6): 414-422 (1966) (CAS abstract 65:11738f), discloses a method for synthesizing EDDS and describes the formation of EDDS complexes with heavy metals. Stability constants were determined for the complexes of EDDS with Cu.sup.2+, Co.sup.3+, Ni.sup.2+, Fe.sup.3+, Pb.sup.2+, Zn.sup.2+, and Cd.sup.2+.
Pavelcik and Majer, Chem. Zvesti. 32(1): 37-41 (1978) (CAS abstract 91(5): 38875f), describes the preparation and properties of the meso and racemate stereoisomer forms of EDDS. The meso and racemate forms were separated via their Cu(II) complexes, with the racemate form being identified from crystallographic data. These compounds are taught to be useful as selective analytical titration agents.
None of these references disclose the compositions of the present invention or recognize the unique fabric stain removal and biodegradability properties of EDDS in the context of laundry detergent compositions.